This invention relates to the recovery of cumene vapors from a vapor stream containing cumene. More particularly, this invention relates to the recovery of cumene from a cumene containing vapor stream using a polymeric adsorbent which is hydrophobic and requires no drying step after steam desorption of the cumene from the substantially exhausted resin.
Phenol is produced commercially by the oxidation of cumene to cumene hydroperoxide followed by the acid hydrolysis of the cumene hydroperoxide to yield phenol. The waste vapor stream which is produced contains unreacted cumene. If desired, in order to recover the unreacted cumene, the vapor waste stream is passed through a vent condenser to remove the bulk of the cumene from the vapor stream. However, substantial amounts of unreacted cumene are not removed by the vent condenser, if used. These substantial amounts of unreacted cumene would, if not removed and prevented from discharging into the atmosphere, present an environmental problem and would result in the loss of valuable starting material for the preparation of phenol.
One method for recovering unreacted cumene from the off gases involves passing the off gases through a bed of activated carbon. The use of activated carbon to remove cumene has not been satisfactory due to the high operating costs associated with the use of activated carbon and resulting from the necessity for frequent rebedding of the carbon. In addition, activated carbon requires excessive amounts of steam in order to regenerate the exhausted activated carbon bed for reuse. Further, during commercial use, activated carbon beds are subject to the attrition of carbon so that adsorbent is lost as a result of this attrition. Moreover, the use of a bed of activated carbon to remove cumene is not efficient due to the fouling of the activated carbon during repeated operation. An additional disadvantage of using activated carbon is that the capacity of activated carbon to adsorb cumene is adversely affected by the presence of moisture so that, after cumene has been desorbed from the activated carbon by the use of steam, the carbon must be dried prior to reuse and, if not dried, the capacity of the activated carbon to again remove cumene, is adversely affected.
U.S. Pat. No. 3,357,158 is directed to the use of certain microporous polymers for making chromatographic separations. This patent discloses the use of a copolymer of divinylbenzene and ethylvinylbenzene for such chromatographic separations. Example 1 of this patent teaches the preparation of a copolymer of divinylbenzene, ethylvinylbenzene and diethylbenzene wherein the copolymer is dried and has a surface area of 700 square meters per gram. The patent, however, relates only to microporous polymers and does not relate to cumene recovery or to steam regeneration of a macroreticular resin.
U.S. Pat. No. 3,805,493 teaches the use of a copolymer of divinylbenzene and ethylvinylbenzene for the removal of vaporous hydrocarbons, for example from motor vehicle fuel tanks and carburators. This patent fails to teach the removal of cumene vapors from a vapor stream containing the same and further fails to teach that a pre-dried polymer of divinylbenzene and ethylvinylbenzene would be useable without a drying step after the desorption of cumene and subsequent reuse to adsorb cumene.
U.S. Pat. No. 3,531,463 teaches the preparation of a divinylbenzene/ethylvinylbenzene polymer and its use as an adsorbent. This patent, however, is not directed to the use of the adsorbent to recover cumene and further fails to teach the utility of a predried divinylbenzene/ethylvinylbenzene copolymer in cumene recovery.
U.S. Pat. No. 4,063,912 is directed to gaseous phase adsorption using partially pyrolyzed polymer particles. This patent discloses the use of partially pyrolyzed macroporous resins for cumene recovery. The patent shows the superiority of the partially pyrolyzed polymer particles to adsorb phenol when compared with a commercial adsorbent. This patent fails to teach that a divinylbenzene/ethylvinylbenzene/styrene polymer which has been predried would be effective in adsorbing cumene, and that, after desorption of the cumene with the steam, the polymer may be used without first drying the polymer.
U.S. Pat. No. 3,798,876 is directed to the abatement of air pollution from organic compounds using polymeric adsorbents. One of the polymeric adsorbents which is used is a copolymer of divinylbenzene and ethylvinylbenzene. This patent also teaches that after regeneration of the resin with steam, the resin is then dried by the sufficient passage of warm air. This patent also teaches that the copolymer of divinylbenzene and ethylvinylbenzene, under the conditions set forth in the patent, is not as effective as activated carbon in removing toluene, a homolog of cumene (column 5, table 4).
It is an object of this invention therefore, to provide a process for the removal of cumene from a cumene-containing vapor stream.
Another object of this invention is to provide a process for such removal of cumene wherein the adsorbent used may be regenerated with steam and may then by reused without the necessity for drying the adsorbent.
Other objects and advantages will become apparent from the following more complete description and claims.